java 模拟浏览器访问网页(转)-优快云博客

本文链接：https://blog.youkuaiyun.com/iteye_19679/article/details/81890614

本文介绍了使用Java的HttpURLConnection下载网页的方法，并解决了访问Google网站被拒绝的问题。通过增加请求方法和User-Agent属性，实现成功访问。同时推荐了更轻量级的HttpConnection方式，并对比了使用HttpClient的性能。

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java 模拟浏览器访问网页

2009-12-04 14:54

正文:

在用Java的HttpURLConnection 来下载网页，发现访问google的网站时，会被google拒绝掉。

        try
         {
             url = new URL(urlStr);
             httpConn = (HttpURLConnection) url.openConnection();
             HttpURLConnection.setFollowRedirects(true);

             // logger.info(httpConn.getResponseMessage());
             in = httpConn.getInputStream();
             out = new FileOutputStream(new File(outPath));

             chByte = in.read();
             while (chByte != -1)
             {
                 out.write(chByte);
                 chByte = in.read();
             }
         }
         catch (MalformedURLException e)
         {
          }
         }

经过一段时间的研究和查找资料，发现是由于上面的代码缺少了一些必要的信息导致，增加更加详细的属性

             httpConn.setRequestMethod("GET");
             httpConn.setRequestProperty("User-Agent","Mozilla/4.0 (compatible; MSIE 6.0; Windows 2000)");

完整代码如下：
    public static void DownLoadPages(String urlStr, String outPath)
     {
         int chByte = 0;
         URL url = null;
         HttpURLConnection httpConn = null;
         InputStream in = null;
         FileOutputStream out = null;

         try
         {
             url = new URL(urlStr);
             httpConn = (HttpURLConnection) url.openConnection();
             HttpURLConnection.setFollowRedirects(true);
             httpConn.setRequestMethod("GET");
             httpConn.setRequestProperty("User-Agent","Mozilla/4.0 (compatible; MSIE 6.0; Windows 2000)");

             // logger.info(httpConn.getResponseMessage());
             in = httpConn.getInputStream();
             out = new FileOutputStream(new File(outPath));

             chByte = in.read();
             while (chByte != -1)
             {
                 out.write(chByte);
                 chByte = in.read();
             }
         }
         catch (MalformedURLException e)
         {
             e.printStackTrace();
         }
         catch (IOException e)
         {
             e.printStackTrace();
         }
         finally
         {
             try
             {
                 out.close();
                 in.close();
                 httpConn.disconnect();
             }
             catch (Exception ex)
             {
                 ex.printStackTrace();
             }
         }
     }

此外，还有第二种方法可以访问Google的网站，就是用apache的一个工具HttpClient 模仿一个浏览器来访问Google

         Document document = null;
         HttpClient httpClient = new HttpClient();

         GetMethod getMethod = new GetMethod(url);
         getMethod.setFollowRedirects(true);
         int statusCode = httpClient.executeMethod(getMethod);

         if (statusCode == HttpStatus.SC_OK)
         {
             InputStream in = getMethod.getResponseBodyAsStream();
             InputSource is = new InputSource(in);

             DOMParser domParser = new DOMParser();    //nekoHtml 将取得的网页转换成dom
             domParser.parse(is);
             document = domParser.getDocument();

             System.out.println(getMethod.getURI());

         }
         return document;

推荐使用第一种方式，使用HttpConnection 比较轻量级，速度也比第二种HttpClient 的快。

转载一些代码，使用HttpUrlConnection来模拟ie form登陆web：

关于java模拟ie form登陆web的问题

HttpURLConnection urlConn=(HttpURLConnection)(new URL(url).openConnection());
urlConn.addRequestProperty("Cookie",cookie);
urlConn.setRequestMethod("POST");
urlConn.setRequestProperty("User-Agent","Mozilla/4.0 (compatible; MSIE 6.0; Windows 2000)");
urlConn.setFollowRedirects(true);
urlConn.setDoOutput(true); // 需要向服务器写数据
urlConn.setDoInput(true); //
urlConn.setUseCaches(false); // 获得服务器最新的信息
urlConn.setAllowUserInteraction(false);
urlConn.setRequestProperty("Content-Type","application/x-www-form-urlencoded");
urlConn.setRequestProperty("Content-Language","en-US" );
urlConn.setRequestProperty("Content-Length", ""+data.length());

DataOutputStream outStream = new DataOutputStream(urlConn.getOutputStream());
outStream.writeBytes(data);
outStream.flush();
outStream.close();

cookie=urlConn.getHeaderField("Set-Cookie");
BufferedReader br=new BufferedReader(new InputStreamReader(urlConn.getInputStream(),"gb2312"));